Analysis of switching, degradation and failure mechanisms by RTN signals in non-filamentary (a-VMCO) RRAM devices

The switching, degradation and failure mechanisms in amorphous-Si/TiO
₂
based non-filamentary (a-VMCO) RRAM device has been analyzed through a combination of random-telegraph-noise (RTN) and constant- voltage-stress (CVS). The pre-existing and generated defects and their impacts have been identified. The amplitude of RTN, which leads to read instability, is evaluated statistically at different stages of cell degradation and correlated with different defects. It is found that the switching between low and high resistance states (LRS and HRS) are correlated with the profile modulation of pre-existing defects in the `defect-less' region near the a-Si/TiO2 interface. The RTN amplitude observed at this stage is small and has a tight distribution. At longer stress times, a percolation path is formed due to defects generation, which introduces larger RTN amplitude and a significant tail in its distribution.